The Applicant's published French patent application FR-A-2 503 442 of Apr. 7, 1981 describes an electric cable having compressed mineral oxide insulation with a sheath and a metal inner conductor being manufactured by successive rolling operations on a preform between cylinders provided with grooves whose width and depth gradually decrease going from one pair to the next, with annealing operations being carried out between the rolling operations. The Applicant has observed that unless special precautions are taken, said method does not provide suitable quality sheathed cables when using ordinary-quality titanium for the sheaths and inner conductors, since the sheath cracks easily.
Preferred embodiments of the present invention overcome the above difficulty and provide an electric cable having compressed mineral oxide insulation and a titanium sheath plus at least one titanium inner conductor which has very good mechanical qualities and satisfactory surface condition and appearance.